The present invention relates to the field of medical devices, particularly catheters. In particular, the present invention relates to a method and device for controlling movement of an elongate shaft for use in the catheterization of a patient, where a portion of the shaft is inserted within the patient.
Angioplasty has gained wide acceptance in recent years as an efficient and effective method for treating types of vascular diseases. In particular, angioplasty is widely used for opening stenoses in the coronary arteries, although it is also used for treatment of stenoses in other parts of the vascular system.
The most widely used form of angioplasty makes use of a dilatation catheter which has an inflatable balloon at its distal end. Using fluoroscopy, the physician guides the dilatation catheter through the vascular system until the balloon is positioned across the stenosis. The balloon is then inflated by supplying a fluid under pressure through a inflation lumen to the balloon. The inflation of the balloon causes stretching of the artery and pressing the lesion into the artery wall to re-establish acceptable blood flow through the artery. In some angioplasty procedures, it may be desirable to use a series of dilatation catheters having different sizes or balloon configurations.
One type of dilatation catheter has a guide lumen provided therein so that a guide wire can be used to establish the path through the stenosis. The dilatation catheter is then advanced over the guide wire until the balloon is positioned across the stenosis. The use of a guide wire enables the catheter to be advanced through the blood vessel relatively quickly, thereby reducing the time required for the procedure.
A "standard" guide wire for use in coronary angioplasty is about 175 cm long while a typical coronary angioplasty catheter is about 150 cm long. When the catheter is in place over the guide wire for use, a portion of the guide wire protrudes proximally from the catheter. The protruding portion enables the guide wire to be manipulated by a physician.
In some instances, it may be desirable to exchange one dilatation catheter (already on the guide wire) for a second dilatation catheter. It is usually preferred that the catheter be removed in a manner which enables the guide wire to remain in place in the blood vessel so that the succeeding catheter may be inserted into the blood vessel, over the guide wire already in place, and guided to the stenosis in the blood vessel. To maintain a guide wire in place while withdrawing the catheter, the guide wire must be gripped at its proximal end to prevent it from being pulled out of the blood vessel with the catheter. The catheter, however, is longer than the proximal portion of the guide wire which protrudes out the patient. Thus, before the catheter is fully withdrawn, it completely covers the proximally extending portion of the guide wire. As a result, there was no means by which a standard guide wire can be held in place to prevent it from being withdrawn together with the catheter. To withdraw the catheter while leaving the guide wire in place, a guide wire with a longer effective length was required.
One means for addressing this difficulty is to use an exchange wire when performing a catheter exchange. An exchange wire may be used initially or may be exchanged for a standard guide wire already in place in the patient. An exchange wire typically is much longer (e.g., 300 cm) than the typical or standard guide wire. The additional length of the exchange wire results in a proximally protruding portion which is longer than the length of the catheter to be removed. When a catheter is removed, some part of the proximally protruding portion of the exchange wire is always exposed to provide a means by which the exchange wire can be gripped and its position in the blood vessel maintained. The succeeding catheter is then inserted into the patient over the exchange wire.
It is generally recognized as undesirable to insert, advance and withdraw a series of guide wires during these types of procedures. Repeated guide wire insertions increase the risk of injury to the patient and also increase the time required for the procedure. It also requires exposure of the patient to additional radiation because of the additional fluoroscopy which is required to properly place the successive guide wires across the stenosis. In addition, long exchange wires are cumbersome and difficult to handle while maintaining the guide wire in place across the stenosis.
Techniques to eliminate the need to change guide wires have been proposed. One solution is the use of a guide wire extension which is attached to the proximal end of the guide wire while the guide wire remains in place in the patient. The guide wire extension effectively increases the length of the guide wire to that of an exchange guide wire. While the technique substantially shortens the duration of the procedure because the extension can be attached at the proximal end of the guide wire much faster than an exchange of guide wires can be performed, the extended guide wire is still cumbersome as the physician is required to handle an extended length of a guide wire outside of the patient during at least a portion of the procedure.
One means for catheter exchange without lengthening the guide wire is by use of a balloon catheter with a guide wire lumen located only adjacent the distal end of the catheter. With this configuration, the guide wire is external to the balloon catheter except adjacent the distal end of the balloon catheter. This catheter arrangement allows the catheter to be withdrawn over the guide wire without requiring the physician to completely release the guide wire until the distal end of the catheter is outside of the patient's body. The guide wire lumen on the catheter is shorter than the length of exposed guide wire, which allows at least some portion of the proximal end of the guide wire to be exposed at all times so that it can be grasped and its position relative to the stenosis can be maintained during removal of the catheter.
Another means for exchanging a catheter without the use of an extended guide wire is to engage the guide wire at a point distally of the catheter and hold it in place relative to the stenosis. This has been done by providing an inflatable guide wire holding balloon which is adapted to be inflated only within a guide catheter. In this arrangement, the dilatation catheter in the patient is withdrawn over the guide wire and inside of the guide catheter a short distance. The guide wire holding balloon is aligned distally relative to the dilatation catheter and is then inflated, thereby "trapping" the guide wire against an inner wall of the guide catheter (and constraining the guide wire from longitudinal movement relative to the guide catheter). The dilatation catheter is then withdrawn over the guide wire (the proximal end of the guide wire can be released) and a second dilatation catheter is placed on the guide wire and advanced along the guide wire to the point where the guide wire is trapped against the guide catheter wall. The guide wire holding balloon is then deflated and the physician advances the second dilatation catheter along the guide wire to the stenosis to continue the procedure. It also has been disclosed that mechanical means such as a wire snare be used within a guide catheter to secure the guide wire thereto, instead of a balloon.
While arrangements have been proposed to facilitate catheter exchanges in guide wire catheter systems without the need for a long guide wire length, they require a modified catheter (no full-length guide wire lumen) or additional components within the patient (e.g., balloon for trapping guide wire within guide catheter). It is desired to devise an arrangement which allows catheter exchanges over a standard length guide wire using a catheter having a full-length guide wire lumen. It is also desired to provide a measurement of the distance the guide wire has moved thus determining the situs of the wire.